o 



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2ii DISCOVERY REPORTS 



62° S some 180 miles short of the ice edge (Station 2812). In 80" W the species extends, in small 

 numbers at least, right to the ice edge (Station 1312). In all the sections for the summer months it 

 can be seen that this species is not common below 250 m. but Table 4 shows that it does extend in 

 small numbers to 1000 m. In each section there is an extension into deeper water in the region of 

 the antarctic convergence, and the same phenomenon has been noticed in other sections not figured 

 here. It may be due to the sinking of the surface waters in this region. 



The main concentration of the species in each line is in the subantarctic, but in 0° there is another 

 concentration south of 60° which is not paralleled in either 90° E or 80° W, though there is a lesser 

 concentration in about 55° S in 90° E and in 63-64° S in 80° W, which is probably comparable with 

 a small concentration between 100 and 50 m. in 55-56° S in 0° Possibly the presence of the Weddell 

 Current in 0° prevents this concentration from being a surface one as are those in 90° E and 80° W. 

 It seems likely that the large antarctic concentration in 0° is a feature unique to that particular area 

 and it is tentatively suggested that its presence is in 

 some way caused by the eddies or swirls between the 

 East Wind and Weddell Drifts which have been already 

 mentioned (p. 209). 



Fig. 4 shows the catches of S. gazellae in 0° plotted 

 against temperature and salinity and indicates how wide 

 a tolerance the species has, though it can be seen that 

 the largest concentrations are restricted to a narrow s ' 

 range of salinity. The concentrations above 20 per = 

 250 m. haul are found between 33-94 and 34-46 %„ with s 

 a temperature range of —0-18° to 11°. , 



Much of this information, together with further 

 details, is given in a separate paper on S. gazellae . 

 (David, 1955). ^ 



S. marri (Fig. 5). The northern limit of this species ., 

 is rather variable, since occasional specimens get "■ 

 carried north by the antarctic intermediate water, but salinity 



the northern limits of the main concentrations are ^ 'g- 4- The relative distribution of the two highest 



orAtTS, oiahunaance 01 S. gazellae ?ind S. serratodentata 

 clearly south of the antarctic convergence. The ;„ the 0° meridian m March plotted against temperature 

 southern limit appears to be the antarctic continental and salinity. The line A! represents the core of the 

 slope. From the three sections shown, the extreme antarctic intermediate water, the two broken lines the 

 northern limits are found to be 431° S in 0°, 48° S in approximate boundaries ofthe warm deep water, and the 



„_ , ^ -.r, r^ ■ r.oTTrrx^i- -1 .• ,• . soHd Une thc CO re of thc South Atlantic Central watCH 



90° E and 63^° S m 80° W. This wide latitudinal 



difference is explicable partly by variations in the latitude of the antarctic convergence, and partly by 



the exceptional absence of any considerable numbers of the species in the subantarctic in the 80° W 



line. It will be seen that the northernmost part of the main concentration in each line is 180 miles 



from the convergence in 80° W, 240 miles from it in 90° E, and 330 miles from it in 0°. The species 



is commonest between 200 and 600 m. but extends in smaller numbers to 1500 m. and occasionally 



more. The subantarctic specimens are never found in the surface layers, that is above 150 m., but they 



may extend to 1500 m. though always in small numbers. In the Antarctic the species is not at all 



uncommon in the surface 100 m., that is, in the antarctic surface water, but this shows only in one of 



the vertical sections, that in 80° W. However, Baker (1955) records S. planctonis ( = <S. marri) in 39 % 



of the N 100 B nets fished in the antarctic surface layers. 



The main concentrations of S. marri are in the warm deep water, as reference to the temperature/ 



